Drive configuration for a skid steered vehicle

Abstract

An electric drive configuration for a skid steered vehicle comprises: a pair of propulsion motors (74a, 74b), each with a motor shaft protruding from both ends of the motor and mounted on the same axis across the vehicle, each being coupled at the outer end to drive one of a pair of tracks or set of wheels of the skid steered vehicle; a control differential steep gear unit (72) positioned between the two propulsion motors and in driveable communication with the inner ends of the two motor shafts: and a steer motor (71) in driveable communication with the controlled differential (72), the steer motor (71) being controllable from zero speed giving straight line running in which both motor shafts are coupled to run at the same speed, to a range of speeds in both directions of rotation giving steering capability in both directions.

Description

[0001]This application is the US national phase of international application PCT / GB02 / 01735, filed 17 Apr. 2002, which designated the US. PCT / GB02 / 01735 claims priority to GB Application No. 0109336.8, filed 17 Apr. 2001. The entire contents of these applications are incorporated herein by reference.BACKGROUND OF THE INVENTION[0002](1) Field of the Invention[0003]The present invention relates to a novel drive configuration for skid steered vehicles, including tracked or wheeled vehicles, for example but not limited to, a military armoured tank.[0004]A skid steered tracked vehicle is steered by forcing the two tracks to run at different speeds (skid steering). In the same way a wheeled skid steered vehicle is steered by forcing wheels to one side of the vehicle to run at different speeds to the wheels on the other side of the vehicle. For tracked vehicles, large driving force differences are required between the two tracks—large braking forces on the inner track and high driving forc...

AI Technical Summary

Benefits of technology

[0016]a pair of drive members for engaging with tracks or wheels of the skid steered vehicle, at least one propulsion motor having a single through motor shaft carrying the motor rotor and protruding from the ends of the motor, a first end of the motor shaft being coupled to one of the pair of drive members and a second end of the motor shaft being coupled to a controlled differential device, and a steer motor in driveable communication with the controlled differential device, the steer motor being controllable from a zero speed to give straight line running to one or more different speeds in either or both directions of rotation enabling steering of the vehicle in at least one direction.

[0019]Desirably, the drive configuration may include a linkage for linking together gear changes and for braking in the transmission system on either side of the vehicle. Various suitable forms of linkage will no doubt occur to the skilled addressee. Linkages may be mechanical; electrical (eg wherein an electrical actuator is used to effect gear changes) or hydraulic (eg when a hydraulic actuator is used to effect gear changes), or of any other suitable form. The provision of a suitable linkage enables simultaneous gear change and / or breaking in the two sides of the transmission system and thereby provides better control in steering the vehicle.

[0020]The controlled differential device preferably comprises of two epicyclical gear trains. In a preferred option the planet carriers of the two epicyclical gear trains are common connected by a shaft running through the two sun gears. The steer motor acts on the two sun gears either through a short cross-shaft two sets of spur gears and a reverse idler gear, or by the use of bevel gears. The two output shafts from the controlled differential device; in this case connected to the propulsion motor shafts, are each coupled to the annuli of the epicyclical gear trains. This arrangement minimises the loads on the connections between the steering motor and the epicyclical gear train, but increases the speed of the planet gears. For cooling and lubrication it therefore may be desirable to consider other possible arrangements as listed below.

[0028]This arrangement greatly simplifies the construction of the motors compared to a system that uses a tubular motor shaft. The gearing, brake and final drive are all easily mounted axially with no requirement to fit inside the run of a cross-shaft. The whole transmission including, gear reductions, gear changes and brakes can be fitted in a cylinder the diameter of the propulsion motors running across the width of the hull, apart from the relatively small steer motor, greatly reducing the volume used by the drive system in the vehicle.

[0031]A feature of this drive arrangement is the use of the controlled differential gear steer unit which causes the transmission of the regenerative steering powers directly through the motor shafts, removes the need for a separate steering cross-shaft and greatly simplifying the packaging and design of the other components.

Problems solved by technology

The system therefore, is not a mechanically regenerating system and has the same disadvantages as a two line system in that oversized motors are required.

A French Patent FR 2,382,362 describes the operation of a controlled differential but does not appear to disclose a practical embodiment of such a device.

Due to the use of bevel gears and the configuration for the two long meshing gears, such an arrangement would need to be large and heavy for a high power device.

The above described arrangements suffer from various disadvantages; including in some cases the need for over-rated motors to achieve steering, complex mechanical arrangements requiring multiple cross shafts and idler gears and / or complex motor configurations incorporating tubular shafts.

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